This invention relates generally to in-mold labeling of plastic containers and, more particularly, to an apparatus and process that cuts non-adhesive labels from a pre-printed roll of label stock more efficiently and that then accurately positions the cut labels on a vacuum conveyor for further processing by conventional pick and place machinery employed in plastic molding processes.
Various in-mold labeling techniques are known in which a label is cut from a roll of label stock and then placed within the cavity of a mold and in which the label becomes adhered to the surface of an article formed within the mold.
U.S. Pat. No. 5,286,317 to Treat et al. describes a mechanism for rotary die cutting labels from a carrier web that is continuously or intermittently moving. An eye mark is provided on the web in association with each of the labels for control purposes while the web is being pulled continuously through the die cutting station by means of driven pinch rolls positioned downstream from the die cutting station.
U.S. Pat. No. 5,344,305 to McKillip describes an apparatus for in-mold labeling in which labels are individually cut from a continuous web as demanded by the cycling of a mold and in which a transfer device picks a freshly cut label from a flat bed or rotary die cutter and places the label within the cavity of a mold located in proximity to the die cutter.
U.S. Pat. No. 5,711,839 to Dronzek, Jr. describes a process for the production of in-line gravure-printed in-mold labeled blow molded containers in which polymeric sheets or rolls are reverse gravure-printed and gravure overcoated on the container-facing side with a heat activatable adhesive and gravure coated on the opposite side with an antistatic coating.
U.S. Pat. No. 5,908,599 to Yoshimi et al. describes a process and apparatus for press punching an adhesive label from a sheet or roll of labels and molding a foamed resin container with the label properly positioned thereon.
U.S. Pat. No. 5,919,414 to Dobler describes a label inserting method and apparatus.
U.S. Pat. No. 5,943,957 to Mason describes a method and apparatus for pad printing inked images onto injection-molded pieces, while they are still in the mold, using a robotics device and an ink transfer mechanism.
U.S. Pat. No. 6,183,238 to Dunlap et al. describes an in-mold labeling system for use with a rotary blow molding machine.
U.S. Pat. No. 6,186,767 to Dunlap et al. describes a label dispensing head for use in a plastic blow molding in-mold labeling system.
U.S. Pat. Nos. 6,422,605 and 6,508,902 to Lind describe an in-mold expanded content label having multiple layers and a heat-activated adhesive, the expanded content label being intended for use in an in-mold labeling process.
U.S. Pat. No. 6,991,261 to Dronzek, Jr. et al. describes labels having a permanent section and a removable coupon section for in-mold production of in-mold labeled molded containers.
The foregoing representative prior art machines and processes variously suffer high label cost, production inefficiencies, and inaccuracies, for example.
An apparatus and process for use in an in-mold labeling application is provided in accordance with the illustrated preferred embodiment of the present invention. The apparatus utilizes a label stock roll containing a multiplicity of pre-printed labels and a pre-printed registration mark associated with each of the labels; a plurality of float rolls and idler rolls that serve to define the path of the label sheet wound on the stock roll before labels are cut therefrom and to maintain a constant tension in the label sheet as it is being unwound, a plurality of sensors along the path to detect the presence of a splice in the label sheet, to detect and laterally justify print patterns on the label sheet, and to detect each of the registration marks on the label sheet for the purpose of aligning the label sheet in a predetermined longitudinal position before labels are cut therefrom; a set of driven pinch rolls for clamping the free end of the label sheet and for longitudinally moving it in a selected direction; a circumferential die cutter for receiving the free end of the label sheet from the pinch rolls and for cutting one or more labels or sets of labels from the label sheet; a passive float roll positioned proximate the output end of the die cutter, the float roll being subjected to a downward force sufficient to create a controlled loop in the label sheet for maintaining a constant tension therein as it exits the die cutter and for permitting the die cutter to operate independently of a vacuum conveyor positioned to receive the label sheet from the float roll; a sensor positioned adjacent the input end of the vacuum conveyor for detecting each of the registration marks for enabling alignment of the label sheet in a predetermined longitudinal position of registration on the vacuum conveyor; a plurality of vacuum plenums provided along the vacuum conveyor, a hold-down vacuum being selectively applied to the vacuum plenums from an external source for maintaining the label sheet in its position of registration on the vacuum conveyor during conveyance to a predetermined label removal position, the hold-down vacuum then being released to permit removal, by an external pick and place device, of one or more of the labels previously cut by said die cutter. One or more scrim hold down assemblies may be mounted along the vacuum conveyor above the label sheet, each of the scrim hold down assemblies being vertically movable between an up position in which it is raised a sufficient distance above the label sheet to permit it to be freely longitudinally conveyed on the vacuum conveyor and a down position in which it contacts the scrim area of the label sheet to permit removal of one or more of the labels previously cut by the die cutter without disturbing the scrim area.